Explanation

Gullible means easily deceived or naïve. This is a game many people play with each other "Whoa, someone wrote 'gullible' in the sky!" "Did you know when you look at the Microsoft logo upside-down it looks like the word 'gullible'?" Those that are gullible have to check. Those that aren't, don't, in fact they will pointedly not do the thing that the first person has suggested (try to look at the Microsoft logo upside down, look up at the ceiling) as a show of how non-gullible they are. Black hat uses this to his advantage to cover up copious bloodstains on a ceiling.

Discussion

It could be a reference to the ASDF Videos... 108.162.250.237 12:31, 13 April 2014 (UTC)

Eeeeeeeeeexcept that asdfmovie 2 (the one which includes the "it says gullible on the ceiling" sketch) was first uploaded in January 2010 ... a good 11 months after this comic was published. Given the style and timeline of the asdfmovie shorts, it's rather more likely that they were (as a whole!) inspired by xkcd, not the other way around... 141.101.70.163 15:45, 17 June 2014 (UTC)

Actually it's a really, really old practical joke. Note how cueball is clearly familiar with the gag and doesn't 'fall for it'. 108.162.246.215 15:30, 21 August 2014 (UTC)

In Fastest-Growing we do not even see "Rob" so we do not even know if this is the Cueball Rob... Also just because Black-Hat nows a Rob in one comic this doesn't mean he is his room-mate. --Kynde (talk) 13:18, 15 March 2015 (UTC)

Changed "gaze" in the explanation to "glance", which makes more sense. -Pennpenn 162.158.2.221 04:21, 15 June 2015 (UTC)

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